1. Field of the Invention
The present invention relates to a shielding case from which a leader terminal is led out from a printed circuit board in a cabinet of high-frequency equipment such as a television tuner.
2. Description of Related Art
In a television tuner or other high-frequency equipment, a circuit board on which circuit components have been mounted is housed a cabinet, namely, a shielding case, constituted primarily by a frame, a top cover, and a bottom cover in order to shut out unwanted signals coming from outside and to prevent internal signals from leaking out.
FIG. 6 is a schematic representation illustrating a conventional shielding case.
As shown in FIG. 6, the shielding case is provided with: a frame 1 which constitutes the peripheral side surface of the shielding case, leaving the top and bottom open; a top cover 4 and a bottom cover 5 which are fitted to both open edges of the frame 1 and which respectively cover open sections 2 and 3 of the frame 1; a printed circuit board (hereinafter referred to as "PCB") 7 which is housed and installed in a cabinet 6 composed by the frame 1, the top cover 4, and the bottom cover 5; and a feed-through capacitor 11 which has one end thereof passed through a hole 8 formed in the frame 1 and further inserted in an inserting hole, not shown, of the PCB 7 and attached by solder 9 and the other end thereof led out of the frame 1, i.e. the cabinet 6, and which has a fixing portion 10 secured to the frame 1.
The feed-through capacitor 11, which is also called a "feed-through type ceramic capacitor," is employed to shield circuitry so as to prevent the leakage of high-frequency power in a high-frequency amplifier, a high-frequency oscillator, or the like; it is provided to short-circuit high-frequency signals to the ground when introducing DC power through a shielding plate. An external electrode of the feed-through capacitor 11 is screwed to or directly soldered to the shielding plate. The feed-through capacitor of this type has a relatively large capacitance and it is expected to provide satisfactory grounding effect even in the VHF band.
In the conventional example illustrated in FIG. 6, the hole through which the feed-through capacitor 11 is inserted is provided in the frame. In another conventional example set forth below, the hole through which the feed-through capacitor 11 is provided in the bottom cover 5, or the top cover 4.
FIG. 7 is a schematic representation showing another conventional shielding case.
As shown in FIG. 7, the shielding case is equipped with: a frame 1 which constitutes the peripheral side surface of the shielding case, leaving the top and bottom thereof open; a top cover 4 and a bottom cover 5 which are fitted to both open edges of the frame 1 and which respectively cover open sections 2 and 3 of the frame 1; a PCB 7 which is housed and installed in a cabinet 6 composed by the frame 1, the top cover 4, and the bottom cover 5; and a feed-through capacitor 11 which has one end thereof passed through a hole 12 formed in the bottom cover 5 or the top cover 4 and further inserted in an inserting hole, not shown, of the PCB 7 and attached by solder 9 and the other end thereof led out of the bottom cover 5, i.e. the cabinet 6, and which has a fixing portion 10 secured to the bottom cover 5.
In the conventional examples described above, however, since the fixing portion 10 of the feed-through capacitor 11 is secured to the outer surface of the frame 1 or the bottom cover 5, the fixing portion 10 juts out of the cabinet, making it difficult to reduce the installation space. In the conventional example shown in FIG. 6, the feed-through capacitor 11 is installed through the hole 8 of the frame 1, making it difficult to install it from above or under the frame 1. This has been making it difficult to achieve automated assembly.